Human LPP gene is fused to MLL in a secondary acute leukemia with a t(3;11) (q28;q23).

The mixed lineage leukemia, MLL, gene is frequently rearranged in patients with secondary leukemia following treatment with DNA topoisomerase II inhibitors. By FISH and Southern blot analyses we identified a rearrangement in the MLL gene due to a novel t(3;11)(q28;q23) chromosomal translocation in a patient who developed AML-M5 3 years after treatment for a follicular lymphoma. Through inverse PCR, the LPP (lipoma preferred partner) gene on 3q28 was identified as the MLL fusion partner. LPP contains substantial identity to the focal adhesion protein, zyxin, and is frequently fused to HMGIC in lipomas. The breakpoint occurred in intron 8 of MLL and LPP. Two in-frame MLL-LPP transcripts, which fuse MLL exon 8 to LPP exon 9, were detected by RT-PCR, although the smaller of these contained a deletion of 120 bp from the MLL sequence. The predicted MLL-LPP fusion protein includes the A/T hook motifs and methyltransferase domain of MLL joined to the two last LIM domains of LPP. A reciprocal LPP-MLL transcript, predicted to include the proline-rich and leucine zipper motifs, and the first LIM domain of LPP were also detected by RT-PCR. In summary, LPP is a newly identified MLL fusion partner in secondary leukemia resulting from topoisomerase inhibitors. The MLL-LPP and LPP-MLL predicted proteins contain many of the features present in other MLL rearrangements.

Persistence of BCR-ABL genomic rearrangement in chronic myeloid leukemia patients in complete and sustained cytogenetic remission after interferon-alpha therapy or allogeneic bone marrow transplantation.

In recent years, the prognosis of chronic myeloid leukemia (CML) has been greatly improved either with interferon-alpha (IFN-alpha) therapy or allogeneic bone marrow transplantation (BMT). In the present study, minimal residual disease was evaluated in 21 patients in complete cytogenetic response (CCR) after such treatments. Samples from bone marrow aspirates or peripheral blood or both were analyzed by conventional cytogenetics, Southern blot, interphase fluorescent in situ hybridization (FISH), and quantitative reverse transcription-polymerase chain reaction (Q-RT-PCR). In all patients, FISH detected 1% to 12% nuclei with a BCR-ABL fusion gene, whereas Q-RT-PCR experiments were negative or weakly positive. Based on these results, we hypothesize that the BCR-ABL genomic rearrangement persists unexpressed in nonproliferating cells whatever the treatment (IFN-alpha or BMT). These data point to the need for follow-up of CML patients in CCR over an extensive period at the DNA level (FISH) to evaluate the residual disease and at the RNA level (Q-RT-PCR) to estimate the risk of relapse. (Blood. 2000;95:404-408)

Does BCR-ABL genomic rearrangement persist in CML patients in complete remission after interferon alpha therapy?

Cytogenetic, interphase fluorescent in situ hybridization (FISH) and RT-PCR methods were used to study minimal residual disease in peripheral blood stem cells collected for autografting in three chronic myeloid leukemia (CML) patients in sustained complete cytogenetic remission after treatment with interferon alpha (IFNalpha). Karyotypic analysis failed to reveal Ph-positive metaphases. FISH detected 9-16% nuclei with a BCR-ABL fusion gene, contrasting with RT-PCR, performed in two cases, which was negative in one case and weakly positive in the other. RT-PCR was also subsequently weakly positive in the third patient. This discrepancy suggests that the BCR-ABL genomic rearrangement persists unexpressed in quiescent cells. These preliminary results, which need to be confirmed in larger series, suggest that monitoring residual disease in CML should be performed both at DNA and RNA levels. Moreover, autografting following IFNalpha therapy should be considered with caution because of the persistence of the BCR-ABL genomic rearrangement in a sizeable proportion of the cells.

Central nervous system relapses after autologous stem cell transplantation for myeloma. Report of two cases.

We report on two cases of central nervous system (CNS) relapse after high-dose chemotherapy and autologous stem cell transplantation. A 55-year-old man received two courses of vincristin, doxorubicin and dexamethasone (VAD) as an induction treatment for stage IIIB IgG kappa multiple myeloma. Bone marrow stem cell collection was performed after a high-dose melphalan (HDM) course (140 mg/m2). Autologous bone marrow transplantation (ABMT) was performed with this cryo-preserved unpurged bone marrow sample after a second HDM course. Three months after ABMT, the patient presented with signs of central nervous involvement with plasma cells and monoclonal IgG kappa in the cerebral fluid. The patient died despite systemic and intrathecal chemotherapy. A 50-year-old man was initially treated with 3 courses of VAD for a stage IIIA IgD lambda multiple myeloma. Blood stem cell were collected after a course of high-dose etoposide and cyclophosphamide. ABMT was performed after total body irradiation (TBI) and HDM. Three months later, he presented with right leg palsy and a lumbar puncture showed numerous plasma cells and the presence of the IgG lambda. The patient died of neurological complications three months later. Extramedullary occurred prior to medullary relapse in the two cases, suggesting the presence of an extramedullary clone of plasma cells with a high degree of chemo-resistance. Although high-dose chemotherapy appears promising, this therapeutic approach could allow the occurrence of presently unobserved complications. Wether CNS prophylaxis is indicated in this context, as recommended in leukemia, remains an open question.